Droplet actuators are used to conduct a variety of droplet operations. A droplet actuator typically includes two substrates separated by a gap. The substrates include electrodes for conducting droplet operations. The gap between the substrates is typically filled with a filler fluid that is immiscible with the fluid that is to be subjected to droplet operations. Droplet operations are controlled by electrodes associated with one or both of the substrates.
In many locations around the world, newborn infants are routinely tested for various genetic conditions. However, the tests are expensive and typically only a small fraction of possible disorders are included in the testing regimen. For example, there are at least 50 lysosomal storage diseases that are rarely tested. Some of these conditions are extremely rare. Pathologies often involve significant physical and mental debilitation leading to death. Therapies are available in some cases. Outcomes may be improved with early treatment. One such disease is Pompe's disease, which results from a deficiency in alpha-glucosidase. Enzyme replacement therapy is available for treating the condition. However, newborns are rarely screened for Pompe's.
With respect to conditions that are tested in newborn infants, testing typically involves collecting a sample of blood is removed from the heel of a baby. The sample is placed on a card, dried, and sent to a central laboratory for testing. The dried blood sample is typically about 6 millimeters (mm) in diameter. The dried blood sample is tested for an indicator of several diseases. Using current methodologies, a prohibitively large volume of blood would be required in order to do a significantly larger number of tests.
There is a need for testing methods that are highly sensitive and require only a small volume of blood. There is a need in the art for improved methods of conducting enzymatic assays using droplet actuators. There is also a need in the art for methods of conducting enzymatic assays that significantly speeds up the time from sample collection to result.